Method in the manufacture of boards of fibrous or/and plastic material

ABSTRACT

A MEANS AND METHOD FOR MAKING BOARD COMPOSED OF FIBERS, SYNTHETIC RESINS AND MIXTURES THEREOF BY PRESSING THE MATERIAL IN A HOT PRESS INCLUDING A GLAZING PLATE WHICH HAS A MATERIAL-CONTACTING SURFACE COMPOSED OF A FILM THAT IS DETACHABLY SECURED TO SUCH SURFACE BY AN ADHESIVE OF SUCH A NATURE THAT IT PERMITS THE EASY STRIPPING AWAY OF THE FILM WHEN DESIRED.

United States Patent 3,689,347 METHOD IN THE MANUFACTURE OF BOARDS OFFIBROUS OR/ AND PLASTIC MATERIAL Rolf Berti! Reinhall, Lidingo, andSteiner Vardheim,

Roslags Nasby, Sweden, assignors to Defibrator Aktiebolag, Stockholm,Sweden NmDrawing. Filed June 18, 1968, Ser. No. 737,846 Claims priority,application Sweden, June 19, 1967, 8,662/67 Int. Cl. B32b 9/00 US. Cl.156-289 3 Claims ABSTRACT OF THE DISCLOSURE A means and method formaking board composed of fibers, synthetic resins and mixtures thereofby pressing the material in a hot press including a glazing plate whichhas a material-contacting surface composed of a film that is detachablysecured to such surface by an adhesive of such a nature that it permitsthe easy stripping away of the film when desired.

This invention relates to an improved method for the manufacture ofboards made of fibres or/and plastic materials.

More particularly this invention relates to a means and method for themanufacture of boards of fibres and/or plastic materials in hot pressesin which glazing plates are used in order to impart to the board asurface structure of the even, finely polished surface of the glazingplate.

When the material to be pressed consists of wet sheets of cellulosepulp, for example, it is subjected in the hot press to high pressure andso high a temperature that water present in the pulp is removed whilethe pulp fibres are bonded together in a board. Normally, the wet sheetis held on its face remote from the glazing plate by a wire screen or aperforated sheet which renders possible the withdrawal of the evaporatedwater from the wet sheet.

Methods of this kind used hitherto have the drawback that particlesoriginating from the material to be pressed deposit on the glazing plateand after a number of pressing operations they reduce the evenness ofthe surface of the glazing plate to such a degree that the manufacturedboards cease to have acceptable surface properties. For this reason theglazing plate must be demounted from the press at regular intervals inorder to be cleaned and repolished. This requires an exchange of glazingplates which is time wasting and causes considerable interruptions inthe production line.

One main object of the invention is to provide a process in which thesedrawbacks are eliminated. According to one main feature of the inventionthe glazing plate is on its surface facing the material to be pressed,coated with a film and kept detachably connected therewith by means of anon-curable adhesive.

This film can be used a plurality of times and then in a very easymanner can be removed by being peeled off from the glazing plate bymeans of a tape, for example. Thus the plate proper need not bedemounted from the press and the interruption of operation causedthereby is avoided. The film may be made of some suitable plasticPatented Sept. 5, 1972 material, paper, metal, or similar material. Aparticularly suitable material is paper that has been coated with ametal having the form of an aluminum sheeting, for example. The coatingfilm as well as the adhesive must be of such type that they withstandthe curing temperatures used in the process of manufacturing the boards.These temperatures may be in the range of to 200 and even reach 250 C.and still more. The binding power of the adhesive should not be greaterthan will permit removal of the film by peeling off after it has becomedirty and needs replacement. An example of a well suited adhesive is thebonding agent or pressure-sensitive type activated by pressure, such asis used in conventional pressure-sensitive tapes.

It is possible to introduce between the plates in a hot press of thesingle or the multi-layer type wet sheets which at their top face can bebounded by the glazing plate covered with the coating film according tothe invention and at the bottom face by a wire screen or perforatedmetal sheet or the like. When applying a new coating film, this film canloosely be placed on the top surface of the material to be pressed andintroduced between the plates and then be bonded to the overlyingglazing plate in the subsequent pressing operation. In case the filmconsists of paper coated with a metal sheeting, the paper to be providedwith the adhesive must be turned so that its adhesive carrying surfaceis uppermost facing the overlying glazing plate.

The boards manufactured according to the invention can be laminated orsheeted. They may consist of fibrous material intermixed with plastic orresin or, if desired, be constituted by plastic material solely.

While several more or less specific embodiments of the invention havebeen described, it is to be understood that this is for purpose ofillustration only, and that the invention is not to be limited therebybut its scope is to be determined by the appended claims.

What we claim is: 1. The method of forming sheet material from a mass ofparticulate material selected from the group consisting of fibers,synthetic resins, and mixtures thereof, which comprises subjecting saidmass to elevated temperatures and mechanical pressure between twoopposed surfaces, at least one of said surfaces constituting a glazed,imperforate surface, the other of said surfaces being a perforatesurface permitting escape of water and steam from said mass under theaction of said temperatures and pressure applied to said mass, andpreventing particles having their origin in said mass from adhering tosaid glazed surface under the influence of said elevated temperaturesand mechanical pressure, said prevention of said adherence beingeffected by applying to said glazed surface a sheet of material selectedfrom the group consisting of paper, metal, and metal coated paper andhaving a film of pressure-sensitive adhesive on the surface thereof incontact with said glazed surface, said sheet being characterized by itsability to be readily peelable intact from said glazed surface.

2. The method of claim 1, wherein said sheet of material applied to saidglazed surface comprises a layer of metal coated paper.

3 3. The method of claim 1, wherein said sheet of matemetal.

rial applied to said glazed surface comprises a layer of 3,228,0913,236,714

References Cited 3,256,121

UNITED STATES PATENTS Loetscher 156-289 Landgraf 156-323 Paulsen 156-323McCullough et a1. 156-323 10 Soehner 156-323 Russell 156-289 4Michaelson et a1. 156-289 Rice et a1. 156-289 Traut 156-323 Abell156-622 Hale et a1. 156-289 CARL D. QUARFORTH, Primary Examiner F. M.GITTES, Assistant Examiner US. Cl. X.R.

